- Three experiments evaluated the effects of different management strategies on immune function and performance of feeder cattle. The objective of experiment 1 was to compare the effects of anticipating, delaying, or vaccinating against Bovine Respiratory Disease (BRD) at the time of weaning and feedlot entry on growth, DMI, and plasma antibody parameters of feeder cattle. The objective of experiment 2 was to evaluate the effects of Cu, Mn, Zn, and Co supplementation, either as inorganic or organic complexed sources, during a 45-day preconditioning program on productive, immunity, and physiological parameters of cattle through preconditioning followed by a 58-day feedlot receiving period. The objective of experiment 3 was to evaluate the effects of supplementing Omnigen-AF or Immune Primer formula products on performance, health, and physiological responses of receiving cattle.
In experiment 1, 90 Angus × Hereford calves were ranked by sex, BW, and age, and assigned to 1 of 3 vaccination schemes against the BRD complex: 1) vaccination at weaning (d 0) and booster at feedlot entry (d 30; CON, n = 30), 2) vaccination 15 d before weaning (d -15) and booster 15 d before feedlot entry (d 15; EARLY, n = 30), and 3) vaccination 15 d after weaning (d 15) and booster 15 d after feedlot entry (d 45; DELAYED, n = 30). From d -15 to 7, calves were maintained as a single group on pasture. On d 8, calves were placed into 1 of 18 drylot pens (6 pens/treatment; 5 calves/pen) and fed alfalfa-triticale hay. On d 29, calves were transported 1,440 km in a livestock trailer and unloaded on d 30 at the same feedyard with the same pen arrangement used prior to transport. From d 30 to 75, calves were fed a receiving diet based on alfalfa-triticale hay + corn-based concentrate. Calf BW was recorded on 2 consecutive days (d -15, -14, 0, 1, 28, 29, 75, and 76). Blood samples were collected on d -15, 0, 15, 30, 45, 60, and 75. The EARLY calves had less (P ≤ 0.09) ADG pre-weaning (d -15 to -1), however had greater (P ≤ 0.01) ADG during feedlot receiving (d 30 to 75) compared to the other treatments. During preconditioning (d 0 to 29), CON had greater (P ≤ 0.04) DMI compared with EARLY and DELAYED. During feedlot receiving, no treatment differences were detected (P ≥ 0.17) for hay or concentrate DMI, G:F, morbidity, and mortality rates. There were no treatment effects on calf BW at weaning, and at the end of preconditioning or receiving periods (P ≥ 0.65). Plasma concentrations of antibodies against Mannheimia haemolytica were greater (P ≤ 0.05) in EARLY vs. CON and DELAYED on d 0, greater (P ≤ 0.04) for CON vs. EARLY and DELAYED on d 15, greater (P ≤ 0.02) in DELAYED and EARLY vs. CON on d 30, and greater (P = 0.03) in EARLY vs. CON on d 75. Plasma concentrations of antibodies against bovine viral diarrhea viruses were greater (P ≤ 0.04) in EARLY vs. CON and DELAYED on d 15, and greater for EARLY and CON vs. DELAYED on d 30 and 45. Collectively, EARLY calves had greater plasma concentrations of antibodies against the evaluated pathogens at feedlot entry, and increased ADG during receiving compared with CON and DELAYED cohorts.
In experiment 2, 90 Angus x Hereford calves were weaned at 7 mo (d − 1), sorted by sex, weaning BW and age (261 ± 2 kg; 224 ± 2 days), and allocated to 18 drylot pens (one heifer and four steers per pen) on day 0; thus, all pens had equivalent initial BW and age. Pens were randomly assigned to receive a corn-based preconditioning concentrate containing: (1) Cu, Co, Mn and Zn sulfate sources (INR), (2) Cu, Mn, Co and Zn complexed organic source (AAC) or (3) no Cu, Co, Mn and Zn supplementation (CON). From day 0 to 45, cattle received concentrate treatments (2.7 kg/animal daily, as-fed basis) and had free-choice access to orchardgrass (Dactylis glomerata L.) long-stem hay and water. The INR and AAC treatments were formulated to provide the same daily amount of Co, Cu, Mn and Zn at a 50-, 16-, 8- and ninefold increase, respectively, compared with the CON treatment. On day 46, cattle were transported to a commercial feedlot, maintained as a single pen, and offered a free-choice receiving diet until day 103. Calf full BW was recorded on days − 1 and 0, 45 and 46, and 102 and 103 for average daily gain (ADG) calculation. Liver biopsy was performed on days 0 (used as covariate), 22 and 45. Cattle were vaccinated against respiratory pathogens on days 15, 29 and 46. Blood samples were collected on days 15, 29, 45, 47, 49, 53 and 60. During preconditioning, mean liver concentrations of Co, Zn and Cu were greater (P ≤ 0.03) in AAC and INR compared with CON. No treatment effects were detected (P ≥ 0.17) for preconditioning feed intake, ADG or feed efficiency. No treatment effects were detected (P ≥ 0.48) for plasma concentrations of antibodies against M. haemolytica, bovine viral diarrhea types 1 and 2 viruses. Plasma haptoglobin concentrations were similar among treatments (P = 0.98). Mean plasma cortisol concentration was greater (P ≤ 0.04) in CON compared with INR and AAC. No treatment effects were detected (P ≥ 0.37) for cattle ADG during feedlot receiving.
In experiment 3, 108 Angus × Hereford steers, originating from 7 cow–calf were obtained from an auction yard on d −2 and transported by road (800 km; 12 h) to an experimental feedlot facility. Upon arrival on d −1, shrunk BW was recorded and steers were grouped with free-choice access to grass hay, mineral supplement, and water. On d 0, steers were ranked by source and shrunk BW and assigned to 1 of 18 pens (6 steers/pen). Pens were allocated to 1) no immunomodulatory ingredient supplementation during feedlot receiving (CON), 2) supplementation with OmniGen- AF (OMN; 22 g/steer daily, as-fed basis; Phibro Animal Health Corp., Teaneck, NJ) from d 0 to 30, or 3) 2 oral capsules of Stocker Immune Primer on d 0 + 15 g/ steer daily (as-fed basis) of Stocker Preconditioned Premix (Ramaekers Nutrition, Santa Cruz, CA) from d 7 to 30 (IPF). From d 0 to 80, steers had free-choice access to grass hay and water and received a corn-based concentrate. Feed DMI was recorded from each pen, and steers were assessed for BRD signs daily. Steers were vaccinated against BRD pathogens on d 0 and 21. Final shrunk BW was recorded on d 81, and blood samples were collected on d 0, 3, 7, 10, 14, 21, 31, 42, 56, and 73. Steer ADG and final BW were greater (P ≤ 0.05) in CON steers than in OMN and IPF steers [1.23, 0.76, and 1.06 kg/d (SEM = 0.06), respectively, and 320, 282, and 307 kg (SEM = 4), respectively] and (P < 0.01) in IPF steers than in OMN steers. No treatment effects were detected (P ≥ 0.76) for BRD incidence (66 ± 4%) and DMI, whereas G:F was greater (P < 0.01) in OMN steers than in CON steers. Mean plasma cortisol concentration was greater (P = 0.01) in CON steers than in OMN and IPF steers. Plasma haptoglobin concentrations tended (P = 0.10) to be greater in CON steers than in IPF steers on d 3, were greater (P = 0.04) in IPF steers than in CON steers on d 7, and tended (P = 0.10) to be less in OMN steers than in IPF and CON steers on d 21. Blood mRNA expression of interleukin 8 was greater (P ≤ 0.05) in OMN and IPF steers than in CON steers on d 3 and in OMN steers than in CON and IPF steers on d 14. Blood mRNA expression of tumor necrosis-α was greater (P ≤ 0.05) in OMN and IPF steers than in CON steers on d 10. Plasma IGF-I concentrations, serum antibody titers to BRD pathogens, and blood mRNA expression of chemokine ligand 5, cyclooxygenase 2, interleukin 8 receptor, and L-selectin did not differ (P ≥ 0.21) among treatments.
Collectively, anticipating initial and booster vaccination against respiratory pathogens to provide both doses prior to feedlot entry appears to be a valid strategy to enhance cattle health and performance during feedlot receiving. Regarding mineral supplementation, INR and AAC increased liver concentrations of Co, Zn and Cu through preconditioning, but did not impact cattle performance and immunity responses during preconditioning and feedlot receiving. Lastly, the immunomodulatory feed ingredients evaluated herein impacted adrenocortical and innate immune responses but failed to mitigate BRD incidence and improve performance of receiving cattle.